/Engine/Source/Runtime/SlateCore/Public/Input/HittestGrid.h
Finds the next focusable widget by searching through the hit test grid
[TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > FindNextFocusableWidget ( const [FArrangedWidget](API\Runtime\SlateCore\Layout\FArrangedWidget) & StartingWidget, const EUINavigation Direction, const [FNavigationReply](API\Runtime\SlateCore\Input\FNavigationReply) & NavigationReply, const [FArrangedWidget](API\Runtime\SlateCore\Layout\FArrangedWidget) & RuleWidget, int32 UserIndex )